Neuroprosthetics: using the power of your mind

Every year, hundreds of thousands of people worldwide lose control of their limbs as a result of an injury to their spinal cord. (Photo: Pixabay.com)

Neuroprosthetics, also known as brain-computer interfaces, are devices that help people with motor or sensory disabilities to regain control of their senses and movements by creating a connection between the brain and a computer. In other words, this technology enables people to move, hear, see, and touch using the power of thought alone. How do neuroprosthetics work? Here is a brief presentation of five major breakthroughs in this field: see how far we have come - and how much farther we can go - using just the power of our minds!

Every year, hundreds of thousands of people worldwide lose control of their limbs as a result of an injury to their spinal cord. In the United States, up to 347,000 people are living with spinal cord injury (SCI), and almost half of these people cannot move from the neck down. For these people, neuroprosthetic devices can offer some much-needed hope.

Brain-computer interfaces (BCI) usually involve electrodes - placed on the human skull, on the brain's surface, or in the brain's tissue - that monitor and measure the brain activity that occurs when the brain "thinks" a thought. The pattern of this brain activity is then "translated" into a code, or algorithm, which is "fed" into a computer. The computer, in turn, transforms the code into commands that produce movement.

Neuroprosthetics are not just useful for people who cannot move their arms and legs; they also help those with sensory disabilities. The World Health Organization (WHO) estimate that approximately 360 million people across the globe have a disabling form of hearing loss, while another 39 million people are blind. For some of these people, neuroprosthetics such as cochlear implants and bionic eyes have given them back their senses and, in some cases, they have enabled them to hear or see for the very first time.

Ear implant

Probably the "oldest" neuroprosthetic device out there, cochlear implants (or ear implants) have been around for a few decades and are the epitome of successful neuroprosthetics. The U.S. Food and Drug Administration (FDA) approved cochlear implants as early as 1980, and by 2012, almost 60,000 U.S. individuals had had the implant. Worldwide, more than 320,000 people have had the device implanted.

A cochlear implant works by bypassing the damaged parts of the ear and stimulating the auditory nerve with signals obtained using electrodes. The signals relayed through the auditory nerve to the brain are perceived as sounds, although hearing through an ear implant is quite different from regular hearing.

Eye implant

The first artificial retina - called the Argus II - is made entirely from electrodes implanted in the eye and was approved by the FDA in February 2013. In much the same way as the cochlear implant, this neuroprosthetic bypasses the damaged part of the retina and transmits signals, captured by an attached camera, to the brain. While Argus II does not restore vision completely, it does enable patients with retinitis pigmentosa - a condition that damages the eye's photoreceptors - to distinguish contours and shapes, which, many patients report, makes a significant difference in their lives.

Retinitis pigmentosa is a neurodegenerative disease that affects around 100,000 people in the U.S. Since its approval, more than 200 patients with retinitis pigmentosa have had the Argus II implant, and the company that designed it is currently working to make color detection possible as well as improve the resolution of the device.

Neuroprosthetics for people with spinal cord injury

Almost 350,000 people in the U.S. are estimated to live with spinal cord injury (SCI), and 45 percent of those who had an SCI since 2010 are considered tetraplegic - that is, paralyzed from the neck down. In much the same way that the cochlear and visual implants bypass the damaged area, so too does this BCI (brain-computer interface) area avoid the "short circuit" between the brain and the patient's muscles created by SCI.

An arm that feels

Other projects on neuroprosthetics have also been carried out, among which is the arm that "feels". Researchers measured the tension in the tendons of the artificial hand that control grasping movements and turned it into electric current. In turn, using an algorithm, this was translated into impulses that were then sent to the nerves in the arm, producing a sense of touch.

Since then, the prosthetic arm that "feels" has been improved even more. The scientists implanted a sheath of microelectrodes below the surface of the patient’s brain - namely, in his primary somatosensory cortex - and connected them to a prosthetic arm that was fitted with sensors. This enabled the patient to feel sensations of touch, which felt, to him, as though they belonged to his own paralyzed hand.